Hypochlorite bleaching of monoelefinic hydrocarbon sulfonates

ABSTRACT

In the reduction of color in an aliphatic sulfonate detergent by heating an aqueous solution containing the sulfonate and hypochlorite bleach, improved decolorization is obtained by concurrently aerating the mixture.

United States Patent [151 3,639,282

Sharman 1 Feb. 1, 1972 [54] l-IYPOCHLORITE BLEACHING 0F [56] Relerences Cited MONOELEFINIC HYDROCARBON SULFONATES lnventor: Samuel H. Sharman, Kensington, Calif.

Assignee: Chevron Research Company, San Francisco, Calif.

Filed: July 1, 1968 Appl. No.: 741,656

U.S.Cl ..252/95,252/l6l,252/353,

260/513 Int. Cl. ..C1ld 1/12 Field of Search ..252/95, l6l, 353; 260/5l3 Attorney-A. L. Snow, F. E. Johnston, G. F. Magdeburger and D. L. Hagmann 5 7 1 ABSTRACT In the reduction of color in an aliphatic sulfonate detergent by heating an aqueous solution containing the sulfonate and hypochlorite bleach, improved decolorization is obtained by concurrently aerating the mixture.

6 Claims, I Drawing Figure PATENTEDIEB 1m? 3.639.282

INVENTOR wry. SHA MAN v ,W

Ai'TRNEYS HYPOCHLORITE BLEACHING OF MONOELEFINIC HYDROCARBON SULFONATES This invention relates to a method for the reduction of color in aliphatic sulfonates. More particularly, it relates to the use of oxygen or oxygen-containing gases concurrently with hypochlorite bleach in the reduction of color in aliphatic sulfonates.

It is known to treat olefin sulfonates with sodium hypochlorite for the reduction of undesirable color present in the sulfonate, particularly where these materials are used as detergents. Thus in British Pat. No. 983,056 the use of hypochlorite bleaches as a means of producing light-colored olefin sulfonates is disclosed. While the process as taught in this reference materially improves the color of the sulfonate, the resulting product nevertheless falls far below acceptable product standards relating to color as established in the art for alkyl benzene sulfonates. There are color bodies present in sulfur-trioxide-derived aliphatic sulfonates which do not ap pear to respond to hypochlorite treatment.

It has now been found that the reduction of color of sulfurtrioxide-derived aliphatic sulfonates is substantially improved in the treatment of an aqueous solution of the sulfonate with hypochlorite bleach by maintaining the reaction medium sub stantially saturated with oxygen gas. Surprisingly, a -20 percent improvement in the color of the resulting bleached sulfonate is experienced when oxygen is dissolved in the medium during the bleaching operation whether or not excess hypochlorite bleach is present in the reaction mixture.

By the term aliphatic sulfonates is meant the sulfonation reaction products obtained from monooleflnic hydrocarbons and sulfur trioxide. These materials are complex mixtures ofa variety of molecular species including alkenyl sulfonates, hydroxy alkane sulfonates, and aliphatic disulfonates. The preparation of such products is described in US. Pat. Nos. 2,061,6l9, 2,06l,620 and 2,094,451, as well as in articles in the detergent trade journals. They are excellent surface-active agents in general, and their use as articles of commerce is especially desirable in view of the fact that the detergent range sulfonates are in general wholly biologically degradable in conventional sewage treatment plants. On the other hand, in view of the vigor of sulfur trioxide in its reaction with monoolefinic hydrocarbons. substantial amounts of color bodies are concurrently produced along with the desired sulfonates, and the relatively poor color of these materials compared to the alkyl benzene sulfonates long known in the detergent art has severely limited the acceptability of the aliphatic sulfonates to the trade.

By detergent-range aliphatic sulfonates is meant by definition the product obtained by the reaction of sulfur trioxide with a monoolefinic hydrocarbon containing from nine to 25 carbon atoms per molecule, including an individual molecular specie and a mixture of molecular species in this range, which is neutralized and/or hydrolyzed following the sulfonation reaction.

In a preferred embodiment, as illustrated in the FlGURE, the bleaching operation is carried out in a stirred tank reactor, 1, fitted for stirring and temperature control. The aqueous sulfonate solution, for example a hydrolyzed C, .,-C,,, n-a-olefin sulfonate containing about 45 weight percent of the sulfonate, is introduced into the reactor via line 2, and sufficient concentrated aqueous sodium hypochlorite to yield a solution in the reactor corresponding to 3 parts (weight) of the bleach per 100 parts of the sulfonate is introduced via line 3. At a basal point in the reactor :1 moderate flow (0.ll.0 cubic foot per gallon per hour) of air is introduced into the liquid reaction mixture via line 4 and is vented from the reactor via line 8. In order to control the natural tendency for foaming of a deter gent solution under the circumstances. a foam inhibition means, for example. recycle pump 5, line 6 and spray head 7, is employed. Bleached sulfonate solution is withdrawn from the reactor via line 9. At 80 C., a preferred bleaching temperature, flow rates in lines 2, 3 and 9 are adjusted to provide for a l bour residence time for bleaching in the reactor.

The temperature-time relationship used in carrying out the present bleaching process varies depending in the main upon the temperature used. At a temperature in the range from about 20 to C. suitable reaction times are in the range I to 3 hours (the longer time corresponds to a lower reaction temperature). On the other hand, at temperatures in the range from about 90 to M5 C., a color reversion effect is encountered and in this range the time for effective color reduction is in general defined by the expression t,--( l47-T)2.28 where r, is the time for start of color reversion and T is temperature in degrees centigrade. At the time t,, the reaction mixture must be quenched, for example by cooling to a temperature below about 90 C., preferably below about 80 C. High-temperature hypochlorite bleaching is the subject of the copending application, U.S. Ser. No. 74l,657 filed July I, l968.

The amount of air or oxygen-containing gas passed into the reaction mixture, i.e., for satisfactory color reduction, is preferably the minimum flow for saturation of the solution with oxygen. Because of the tendency ofthe solution to foam, an excess flow is inconvenient. Because the oxygen concentration in the solution is a function of the partial pressure of oxygen in the atmosphere in contact with the solution, better results are experienced when the system pressure is superatmospheric. However, in view of the relatively high cost of pressure reaction systems, operation at pressures above a few atmospheres, i.e., at 3 to about 5 atmospheres pressure, is usually not economically attractive. A rate of flow of oxygen. air, or an oxygen-containing gas into the bleaching mixture sufficient for some oxygen to be present in the effluent gas stream maintains a useful concentration of oxygen in the solution.

The hypochlorite bleach used in the invention is preferably sodium hypochlorite although alkali metal and alkaline earth metal hypochlorites may also be used. The sodium bleach is an article of commerce and least costly. On the other hand, the alkaline earth bleaches, such as the calcium salt, can be used, but they are less desirable by reason of the unfavorable solubility parameter.

The amount of bleach relative to the sulfonate which is desirably used varies, depending: l upon the intensity of the color of the sulfonate; (2) the particular bleach to be used; and (3) in lesser degree, the temperature to be employed. In general, a satisfactory amount is in the range from about 0.25 to 5 parts (weight) per I00 parts (weight) of the sulfonate. Larger relative amounts. for example 10 parts of bleach, may be used without substantial adverse effects, but in general such use is uneconomical.

The subject aliphatic sulfonates are generally neutralized and hydrolyzed utilizing aqueous sodium hydroxide or the equivalent. Aqueous solutions or an aqueous medium are therefore preferred for the bleaching. However, polar solvents relatively stable to the bleach may also be used such as aqueous alcohol solutions, and the like.

The concentration of the sulfonate in the bleaching solution may vary widely. As a practical matter, at least a l0-weightpercent solution is desirably employed. All of the sulfonate need not be in solution for the bleaching. Thus bleaching is effective where an aqueous slurry of the sulfonate is used. For mechanical and economical reasons, best results in general follow from the use of aqueous solutions containing from about 20 weight percent up to the saturation value, i.e., usually in the range 5065 weight percent, ofthe sulfonate.

The pH of the reaction mixture may be neutral, basic or acidic. The bleaching may be effected concurrently with hydrolysis. The latter is preferably accomplished using alkali. In the preferred mode, the pH will be in the range above 7. Large excesses of acid or base are in general desirably avoided. The sulfonates are used in the main as nearly neutral salts. Thus the excess acid or base has to be neutralized, thereby adding salt to the product.

In general, the aliphatic sulfonates used for feeds in the instant process are those obtained in sulfonations carried out at temperatures below about C., generally below about 50 C., and above about C., for the reasons that color body production is minimal at the lower reaction temperatures.

In general, the sulfonate feeds used in the instant process will be substantially free of aromatic substituents for the reason that aromatic carbocyclic rings are usually sulfonated under conditions analogous to those conditions where sulfur trioxide reacts with an olefinic hydrocarbon. On the other hand, the presence of substantial but minor. i.e., less than 50 percent (mol percent), of an aromatic sulfonate, for example an alkylbenzenesulfonate, does not interfere with color reduction ofthe subject aliphatic sulfonates.

Aliphatic sulfur-trioxide-derived sulfonates in general are satisfactorily treated by the instant process, i.e., with a substantial reduction of the color. As a practical matter suitable sulfonate feeds for the instant process will contain from about nine to 25 carbon atoms, substantial amounts of unsaturation, i.e., carbon-carbon unsaturation. substantial amounts of hydroxy substitution and substantial amounts of aliphatic disulfonates. i.e., it will be a sulfur-trioxide-derived sulfonate. The suitable sulfonate feeds are conveniently described in terms of the olefinic hydrocarbons used to prepare them and these include in general all substantially nonaromatic monoolef'inic hydrocarbons. The preferred sulfonate feeds are those prepared from wolefins, from the n-a-olefins and from internal n-alkenes. Molecular mixtures as well as individual molecular species are satisfactory feeds. These sulfonate compositions are known to the art and are not per se part of the instant invention except as materials whose color properties are improved by the instant process.

Representative olefin sulfonate feeds for the present process include those obtained from C C cracked-wax aolefins, as well as the individual molecular range fractions thereof, C -C -CI-UlfinS, C -C internal n-olefins, C -C internal n-oleftns; branched-chain alkenes such as S-methyl-lhexadecene; other olefins such as cyclooctene, cyclododecene. vinylcyclohexane, dodecene-2, hexadecene- 4 ierpines, eicosene-l, nonene-l, octadecened. 4-methylcyclooctene. hendecene-Z, partially isomerized n-a-olefin, i.e., mainly n-alkene-2's. and the like monoolet'inic, substantially nonaromatic hydrocarbons.

in addition to the use of the above-described preferred means to suppress undesirable foaming, other mechanical means of breaking foam may be used if desired, for example. a paddle or screen rotating in the area above the level of the liquid solution and the like.

The following examples further illustrate the invention. They are not intended as limitations on the invention.

EXAMPLES l-3 in these runs a ZS-weight-percent aqueous solution of a cracked-waxderived n-C, C,.. u-olefin sulfonate which had previously been hydrolyzed with caustic was bleached with sodium hypochlorite at 50 C. for a period of l hour. For each 100 parts (weight) of the sulfonate. the reaction mixture contained 3 parts of sodium hypochlorite. The amount of oxygen introduced into the solution was varied: (l) by varying the stirring rate and 42) by blanketing the reaction mixture with nitrogen. The results were as follows:

Run Condition Klett color value 1 Slow stirring 223 2 Fast I92 3 Fast and nitrogen blanket Color determination made by KlettStimmcrson photoelectric colorimeter These data demonstrate that concurrent aeration of the reaction mixture, for example as where air is introduced into the mixture by the cavitation caused by high-speed stirring, markedly improves hypochlorite bleaching.

When other hypochlorite salts such as calcium or sodium hypochlorite are used, then similar improvements are obtained when oxygen is passed concurrently into the reacting medium.

As will be evident to those skilled in the art, various modifications on this invention can be made or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the following claims.

lclaim:

1. In the process for the reduction of color in a sulfonate by treatment with an alkali or alkaline earth metal hypochlorite in an aqueous solution at a temperature in the range from about 20 to C., wherein the sulfonate is obtained by the reaction of sulfur trioxide with a monoolefinic hydrocarbon having a carbon atom content in the range from about nine to 25, the improvement which comprises introducing an oxygencontaining gas into the aqueous solution, said gas having an oxygen content sufficient for some oxygen to be present in the resulting effluent gas stream.

2. The process as in claim I wherein said gas is air.

3. The process as in claim I wherein the hydrocarbon has a carbon atom content in the range from about nine to 25.

4. The process as in claim 1 wherein the aqueous solution or medium contains in parts by weight for each [00 parts of the sulfonate an amount of said hypochlorite in the range from about 0.25 to 10 parts.

5. In the process for the reduction of color in a sulfonate by treatment with an alkali or alkaline earth metal hypochlorite in an aqueous solution at a temperature in the range from about 20 to 145 C., wherein the sulfonate is obtained by the reaction of sulfur trioxide with a monoolefinic hydrocarbon having a carbon atom content in the range from about nine to 25, the improvement which comprises effecting said treatment in a tank reactor by introducing air into the solution at a rate in the range from about 0.] to 1.0 cubic feet per gallon of said solution, and wherein resultant foaming of said solution is inhibited by spraying a withdrawn portion of said solution into contact with the remainder.

6. The process as in claim 5 wherein said hydrocarbon is an n-a-olefin having a carbon atom content in the range from about 15 to 18.

mg' g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,639 ,282' Datedf Egbnnany 1912 Inventor(s) Samuel harman It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title column 1, line 1, "MONOELEFINIC" should read --MONOOLEFINIC--.

Column 2, line 9, "t =(l 47-T)2.28"-"should read 'shgmu' and sealed this 5th day of September 1972.

(SEAL) Attest:

JDR'AHD i=1 .FLE'I'JILER,JH. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 53 3 UNITED STATES- PATENT OFF-ICE CERTIFICATE OF CORRECTION Patent No. 3,639,282 I Dated Egbnnanil 1 1912 Inv entor(s Samuel- S m n It is certified that error appears in the above-identified. Patent 1 vand that said Letters Patent are hereby correcteda s shown below:

Title column 1, line 1-, "MONOELEFINIC' should r-ead '--.-MONOOLEFINIC--.

Column 2, line 9 "t ,=(l t7 T)2.28 should read -t =.,(1u7 T) 2.28--.

3i; ;n zd and sealed this 5th day of September 1972.

(SEAL) Attest: v

iiDh-VTHD 1-'1.FLI5IJILER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents @33 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,539,282 Dated E h 1922 Inventor(s) Samuel harman It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title column 1, line 1, "MONOELEFINIC" should read -MONOOLEFINIC--.

Column 2, line 9, "t =(l'+7-T)2.28" should read --t (In? T) 2. 28--.

Lji ""1':Ij and sealed this 5th day of September 1972.

Attestt ADUAHD M .FLUIUHBH,JR. ROBERT GOTTSGHALK Attcsting Olficer Commissioner of Patents 

2. The process as in claim 1 wherein said gas is air.
 3. The process as in claim 1 wherein the hydrocarbon has a carbon atom content in the range from about nine to
 25. 4. The process as in claim 1 wherein the aqueous solution or medium contains in parts by weight for each 100 parts of the sulfonate an amount of said hypochlorite in the range from about 0.25 to 10 parts.
 5. In the process for the reduction of color in a sulfonate by treatment with an alkali or alkaline earth metal hypochlorite in an aqueous solution at a temperature in the range from about 20* to 145* C., wherein the sulfonate is obtained by the reaction of sulfur trioxide with a monoolefinic hydrocarbon having a carbon atom content in the range from about nine to 25, the improvement which comprises effecting said treatment in a tank reactor by introducing air into the solution at a rate in the range from about 0.1 to 1.0 cubic feet per gallon of said solution, and wherein resultant foaming of said solution is inhibited by spraying a withdrawn portion of said solution into contact with the remainder.
 6. The process as in claim 5 wherein said hydrocarbon is an n-Alpha -olefin having a carbon atom content in the range from about 15 to
 18. 